In the present day, device fabrication, such as semiconductor device fabrication, may the use of one or multiple sacrificial mask layers, or sacrificial masks, including so-called hard masks. During patterning of devices using hardmasks, such as during three dimensional NAND memory device (3D NAND) and DRAM fabrication, a useful property of the hardmask is etch resistance to the etchant being used to etch underlying substrate features.
Patterning of narrow features (DRAM bitline/wordline patterning) or hard-to-etch materials e.g refractory metals or chalcogenide compounds requires maintaining vertical profiles, including minimal line bending and minimal line edge roughness, during lithography and post-lithography etching of underlying features. In addition, metallic or doped hardmask films may be disfavored, due to possible contamination in a device being patterned, such as a memory device. Known hardmask materials may have density on the order 1.8 g/cm3 to ˜2.4 g/cm3 for materials such as chemical vapor deposition (CVD) of C, physical vapor deposition (PVD) of C, and SiN formed by plasma enhanced chemical vapor deposition (PECVD). These hardmask materials may exhibit insufficient etch selectivity for present day and future technology nodes. As a consequence, a thicker hardmask layer may be needed, impacting critical dimension (CD) control, leading to the inability to pattern small CD features, and the inability to etch material in high aspect ratio structures. Alternatively, physical vapor deposition (PVD) may be used to generate hardmask materials having higher etch resistance, where the etch rate during patterning processes is acceptably low. A characteristic of known hardmask materials exhibiting acceptable etch resistivity, such as PVD hard mask layers, is a relatively high stress. Two results of such high stress in a layer, such as a hardmask layer, is wafer (substrate) bowing, where the bowing may lead to overlay shifts and line bending of patterned features
With respect to the CVD process, the PVD process provides excellent film purity because of the avoidance of byproduct formation and the film formation by direct transport of atoms from the Si target source to the substrate through the gas phase. SiN material deposited by PVD has a higher density of 2.9 g/cc vs ˜2.4 g/cc(cm3) for SiN material formed by CVD, and is close to the bulk density of 3.1 g/cc. The PVD SiN deposition temperature is generally lower in the range 200° C. to 375° C., and no hydrogen is present in SiN films deposited by PVD. For a highly compressive film, the film structure is amorphous, while low stress films exhibit a columnar structure.
With respect to these and other considerations the present disclosure is provided.